Disgrifiad: In 1842 the Metropolitan Commissioners in Lunacy investigated conditions in which pauper lunatics were kept in England and Wales. In 1844 their report revealed the appalling standards of care for Welsh pauper lunatics.

A group of landed gentry, clergy and businessmen in Denbigh formed a committee and held a meeting at the Denbigh General Infirmary in October 1842 'for the purpose of calling attention of the public to the importance of establishing a hospital for the insane in some central part of North Wales'. (HD/1/288) Local land owner Joseph Ablett of Llanbedr Hall gave 20 acres of land, worth £2,000, on which the hospital was to be built. The committee raised money through public subscriptions which included £50 each from Queen Victoria and Prince Albert.

The building of the hospital commenced in 1844, led by architect Thomas Fulljames with the advice and guidance of Dr. Samuel Hitch. In 1847 an agreement was reached with five of the six counties in North Wales; Denbighshire, Flintshire, Caernarvonshire, Merionethshire and Anglesey, who contributed towards the financing of the project. The hospital opened in October 1848 and was known as the North Wales Counties Lunatic Asylum. During the first 100 years the hospital was managed by the Committee of Visitors which consisted of representatives of the five counties and the Subscribers.Within the asylum occupation was seen as a therapy and as a result patients were employed in various capacities, both to aid their recovery and also to support the running of the asylum. Females were employed in the kitchen, and laundry and performed various cleaning duties, whilst male patients were employed in gardening and outdoor work, and later in more industrial crafts as workrooms began to develop.The hospital had its own farm which included herds of pigs and cattle. As well as the production of crops, milk and meat to support the running of the hospital the farm also provided employment opportunities for patients. In 1895 Kings Mill Farm was purchased to add to Parc y Twll Farm. In 1958 the farm was sold, guided by the advice of central government the Board of Control came to the conclusion that asylum farms were no longer appropriate to the needs of a modern hospital.

The hospital regularly suffered from overcrowding and throughout its history a number of extensions were built, and new properties were acquired. In 1862 a new chapel was built with seating for 200 patients, to replace the old chapel rooms on the top floor at the front of the building. In 1865 extensions were built on either side of the back of the building to accommodate a further 150 patients. In 1881 a further extension was built, consisting of a new male wing for 160 patients, a new dining hall to seat 400 and an extension to the chapel which now seated 440. In 1894 to help ease the continued problem of overcrowding it was necessary to rent Glanywern Hall near Llandyrnog to accommodate up to 80 female patients.

In 1897 a temporary annexe to house 100 female patients was built to help ease the overcrowding problem, and building started on a new significant extension which included a new heating system, electric lighting, a new sewage system, and a new water supply. The building programme faced many delays due to disputes with the architects and building contractors who had been hired to carry out the work. By 1905 the extension was fully completed and included a laundry, boiler and engine house, and isolation hospital which opened in 1902, female chronic and epileptic wards which opened in 1903, followed by a male attendant's block, kitchens and dining hall which opened in 1904. By 1905 female staff accommodation, and an administrative block was opened. In 1908 two further blocks were added in 1908 to accommodate 78 male and 74 female patients. These were the final additions to the main building. In the 1920s additional properties were purchased including Gwynfryn house in 1926 to accommodate 25 to 30 females, and Trefeirian house in 1927 to house 20 convalescent males. In 1934 Reception wards opened in Gwynfryn house and the Nurses Home. In 1937 Pool Park Hospital in Ruthin opened, which provided accommodation for 80 patients.

In 1948 under the National Health Service Act the North Wales Counties Mental Hospital became the North Wales Mental Hospital, and the Committee of Visitors was replaced by a new management structure. The new Committee was given the responsibility for managing the Mental Deficiency Institutions of Coed Du, Broughton, Llwyn View in Dolgellau, Fronfraith and later Garth Angharad and Oakwood Park. Following a visit to the hospital by the Minister of Health, Enoch Powell in October 1960, a national strategy to phase out the old style mental hospitals was announced. Despite plans for its eventual closure the hospital continued to develop, and a training school for nurses was opened in 1969. In 1987, as part of the development of locally based smaller mental health services, a ten year strategy was devised to enable to closure of the hospital, Pool Park was closed in 1991, and the main hospital closed in 1995.

The hospital had several names during its lifetime, when it opened in 1848 it was known as the North Wales Counties Lunatic Asylum. With the passing of the Mental Treatment Act in 1930 the asylum officially became a hospital and was known as the North Wales Counties Mental Hospital. After the establishment of the National Health Service in 1948 the hospital became known as the North Wales Hospital for Nervous and Mental Disorders, and was often referred to as the North Wales Mental Hospital. By the time the hospital closed in 1995 it was known as the North Wales Hospital. Informally the hospital was and is often referred to as the Denbigh Asylum or Denbigh Hospital.